Real-time traffic data collection is of fundamental importance for traffic information management, road guidance, and intelligent vehicle highway systems (IVHS).
Most techniques addressing this issue use static probes, i.e. fixed sensors and/or cameras. Given the enormous size of a continental roadway system, and the sheer number of roads contained therein, it is impractical not to mention prohibitively expensive to install sensors and/or cameras throughout the network to collect road traffic data for each and every public road on the continent.
U.S. Pat. No. 6,401,027 (Xu et al.) entitled “Remote Road Traffic Data Collection and Intelligent Vehicle Highway System” discloses a method for collecting road traffic data by using moving vehicles as probes. As described in this patent, vehicles subscribing to the intelligent navigation service periodically transmit position data to a traffic data center which computes traffic conditions and broadcasts this traffic data back to the vehicles. In-vehicle navigation devices then display or otherwise use the traffic information to enable the vehicle occupants to intelligently navigate the roadways to seek the fastest route to their destination, primarily by avoiding traffic congestion. As taught by this above patent, each vehicle maintains only two digitized road network maps at any time, one being the continental expressway network map and the other being a local regional or metropolitan roadway network map. However, even though the foregoing technology can, in theory, cover the entire territory of a continent, the sheer number of links and nodes needed to represent all the roadways and intersections in a continental roadway system is so enormously large that it is computationally inefficient to do so.
Accordingly, there exists a need for a technology that would enable intelligent vehicle highway systems for the entire expanse of a continental roadway network to thereby provide computationally-efficient and seamless intelligent navigation services to vehicles traveling large distances from one portion of a continental roadway network to another.